Concern over human impact on climate change prompted a 1997 United Nations conference in Kyoto, Japan. The resulting Kyoto Protocol seeks to stabilize greenhouse gases in the atmosphere “at a level that would prevent dangerous anthropogenic interference with the climate system.”
Perfluorocarbon compounds (PFC's), hydrofluorocarbon compounds (HFC's), chlorofluorocarbons (CFC's), hydrochlorofluorocarbon compounds (HCFC's), and their like, have been widely used in a broad variety of industrial, commercial, consumer and public use applications and uses. Recently, concern has increased about potential damage to the earth's atmosphere and climate, and certain perfluorocarbon compounds (PFC's), hydrofluorocarbon compounds (HFC's), chlorofluorocarbons (CFC's), hydrochlorofluorocarbon compounds (HCFC's), and their like, have been identified as particularly problematic in this regard, at least in part because of the greenhouse gas effect and relatively high global warming potentials (GWP) associated with those compounds. In view of the relatively high GWP of these compounds there has been a vigorous search for alternative compounds of lower GWP to replace these compounds of higher GWP in those use, application and compositions to be used in such applications and uses.
The entry into force of the Kyoto Protocol on Feb. 16, 2005 has accelerated the need for elimination or greatly reducing the use of GWP compositions. Thus, there is a continual search for new fluorocarbon and hydrofluorocarbon compositions for use, especially in air conditioning and refrigeration uses, so as to reduce global warming and for lessening possible depletion of the ozone layer. There is particularly a need for such new compositions that are essentially non-flammable and essentially non-toxic, and that do not have a deleterious effect on the atmosphere. Hydrofluoroolefin (HFO) propenes have been proposed as candidates for such compositions. However, these HFO propenes are flammable by ASHRAE (American Society of Heating, Refrigerating and Air-Conditioning Engineers, Inc) standards.
Additionally, since the commercial introduction of R-134a (1,1,1,2-tetrafluoroethane) and other similar HFCs, compressors have been engineered to take advantage of their excellent chemical stability. Thus, new low GWP compositions designed for use as refrigerants should preferably have similar stability, as well as being non-flammable and have a boiling point within a reasonable range so that the pressures should be similar to refrigerants now in use. While a number of compositions and mixtures have been proposed as a solution to this problem of developing suitable low GWP working compositions there has not yet been developed a composition or mixture of compositions that has an acceptable combination of boiling point, chemical stability, low GWP and non-flammability. For example, carbon dioxide is an example of a refrigerant that is stable and has low GWP, but whose pressures are significantly higher than refrigerants now in use. This deficiency generates significant problems in attempting to implement its use in the refrigeration industry. Thus, there is still a significant need to develop a composition or mixture of compositions that has an acceptable combination of boiling point, chemical stability, low GWP and non-flammability. The use of single component fluids or azeotropic mixtures, which do not fractionate on boiling and evaporation, is desirable. However, the identification of new, environmentally-safe, non-fractionating mixtures is complicated due to the fact that azeotrope formation is not readily predictable.
The industry is continually seeking new fluorocarbon based mixtures that offer alternatives, and are considered environmentally safer substitutes for CFCs and HCFCs. Of particular interest are mixtures containing both fluoroolefins and other fluorinated compounds, both of low ozone depletion potentials and low global warming potentials. Such mixtures are the subject of this invention.